1. Technical Field
The present invention is related to a method of producing a retro-reflective heat transfer film with a transparent protective sheet for the whole surface thereof, and, in particular, to a retro-reflective heat transfer film excellent in physical durability, flexibility, secondary workability, change-resistance, resistance to ultraviolet rays, water resistance, weather resistance, salt resistance, solvent resistance, etc. without lowering luminance, and uses a transparent TPU sheet 1 as a base substrate instead of normal backing material already produced.
2. Description of the Conventional Method
A retro-reflective sheet is widely used for safety clothes, fire clothes, safety articles, safety equipment, sportswear, shoes, decorations and the like. Thanks to its retro-reflective function when it receives light, it can achieve peculiar design while, because the glass bead layer is exposed on the surface, it lacks in physical durability, thus causing damages in the glass bead layer when friction or impact is applied to lower the capability of retro-reflection and to exhibit bad appearance, disadvantageously resulting in lowering product quality.
The exposed glass beads causes bad change resistance and can be easily removed, and polluted by foreign matters such as dust or fume, etc., causing significantly lowered capability of retro-reflection. In such a case, it is not easy to clean the sheet (because the glass beads can be removed). Significantly reduced resistance to ultraviolet rays lowers the capability of adhesiveness and retro-reflection and in addition causes bad secondary workability and restricts its application to various articles. Additionally, when the retro-reflective sheet is attached to different material or the retro-reflective sheet to leather or rubber, the glass bead layer is easily separated because of its bad adhesiveness, thereby causing products to be rejected and also product durability to be lowered. Therefore, to overcome the aforementioned problems, there is a continuous need for improving the disadvantages.
On the other hand, very heavy and expensive plate-type articles have been devised where a retro-reflective sheet is fixed on the surface of a plate such as safety plates on a road, etc. and the surface of the retro-reflective sheet is then coated thick with transparent urethane or transparent resin, etc. However, such an application is not a transfer sheet that can be applied and available to many products, but is a simple example of application of the retro-reflective sheet. Accordingly it cannot be compared to the invention.